In certain of optical projection video display systems, a mirror array is illuminated from an optical energy source. In such a system, the orientation of each of the mirrors is electronically perturbed to determine a propagation path for a beam of light reflecting from each mirror. The exact path of the reflected beam which passes through a slit determines the intensity of the optical energy which passes therethrough. The optical energy exiting from the slit is then focused upon a screen. Therefore, the orientation of a mirror directing each of the reflected beams through a corresponding slit determines the intensity for each pixel in the display.
Each of the mirrors is controlled by an actuator comprising one or more electrodisplacive, e.g., piezoelectric or electrostrictive members upon which each mirror is mounted. By applying a DC electrical signal to each of the electrodisplacive members, the electrodisplacive members deform, as is well known in the art, to thereby, e.g., tilt the plane of the reflective surface of the mounted mirror. The amplitude of the DC signal controls the degree of the tilting of the mounted mirror. Optical projection video display systems and various configurations of such actuated mirror arrays are disclosed in, e.g., U.S. Pat. Nos. 5,085,497; 5,175,465; and 5,185,660.
In a copending, commonly assigned application, U.S. Ser. No. 08/216,754, entitled "ACTUATOR ARRAY AND METHOD FOR THE MANUFACTURE THEREOF", there is disclosed yet another actuated mirror array which may be used in such optical projection video display systems. FIG. 1 presents a cross sectional view of the actuated mirror array which comprises a substrate 1, an array 3 of actuators, e.g., 30, 30', 30" and a corresponding array 5 of mirrors, e g , 50, 50', 50" . Each of the actuators, e.g., 30, in turn, includes a pair of electrodisplacive members 31a, 31b.
Each electrodisplacive member 31a(31b) has a side surface 32a(32b), a part of a grooved surface 33a(33b), a top surface 34a(34b) and a bottom surface 35a(35b). The side surfaces 32a, 32b of the electrodisplacive members 31a, 31b are in a facing relationship to each other with a first metalization 36 formed therebetween. The grooved surface 33a(33b) is formed between the top surface 34a(34b) of the electrodisplacive member 31a(31b) of the actuator 30 and the top surface 34b'(34a") of the adjacent electrodisplacive member 31b'(31a") of an adjacent actuator 30'(30") with a second metalization 37a(37b) provided thereon. The second metalization 37a(37b) is usually coupled to a common ground potential. On the top surfaces 34a, 34b of the electrodisplacive members 31a, 31b, a mirror 50 is mounted. The bottom surfaces 35a, 35b of the electrodisplacive members 31a, 31b are mounted on the substrate 1.
Prior to the mounting of the actuator 30 on the substrate 1, an opening 11 is formed through the substrate 1 at an intermediate location between the pair of the electrodisplacive members 31a, 31b. A third metalization 12 fills the hole. Further, an electrically conductive adhesive paste 13 is provided on the third metalization 12.
The bottom surfaces 35a, 35b of the electrodisplacive members 31a, 31b are then mounted on the substrate 1 with the first metalization 36 centered around the electrically conductive adhesive paste 13. An addressable driver (not shown) mounted to the lower surface of the substrate 1 may then apply a voltage to the third metalization 12 for a desired tilting of the mirror 50. The voltage may be developed in accordance with the corresponding pixel intensity in an optical projection video display system of the type disclosed in the above-referenced U.S. Pat. No. 5,185,660.
In such actuators, however, the contact resistance between the first metalization 36 and the third metalization 12 can be undesirably increased due to a possible uneven distribution of the conductive particles in the paste 13, which may render inadequate or improper the tilting operation of the mirror 50 upon application of such voltage to the third metalization.